This invention concerns a track for drawing assemblies, used preferentially on drawing machines for metal products, such as bars or tubes, the drawing machines comprising two opposite and counter-rotating tracks suitable to achieve the axial drawing of said metal products.
The invention also concerns the connected method to remove and to replace the gripping elements associated with said tracks.
In the following description, to simplify the explanation, the metal products will be referred to under the general term of xe2x80x9cbarsxe2x80x9d, irrespective of the section thereof (round, square, polygonal, etc.) and of the fact that they are hollow or solid.
The state of the art includes drawing machines for metal bars in which the drawing assembly comprises two tracks counter-rotating and opposite each other with respect to the drawing axis, each one consisting of a plurality of links on which pads are mounted to grip the bar to be drawn.
Each gripping pad has a hollow shaped to mate with the section of the bar in its already drawn segment. The two tracks are made to rotate continuously and, in co-operation with relative rigid guides, are suitable to clamp and draw the bar to achieve the drawing process.
The gripping pads can be removed from the respective links, so that they can be removed in the event of wear or if the section of the bar is changed.
The state of the art includes gripping pads which have two faces, a front and a rear face, inclined and suitable to cooperate with the walls of mating xe2x80x9cdove-tailedxe2x80x9d seatings made on the links of the track. The gripping pads are mounted by inserting them inside the relative xe2x80x9cdove-tailedxe2x80x9d seatings and they are subsequently clamped by means of rapid attachment/detachment means provided for this purpose and associated with the links of the track.
Generally speaking, the rapid attachment/detachment means consist of a pair of lateral clamps, associated with relative elastic means, suitable to clamp the sides of the gripping pads and prevent them from coming off.
In a condition of association with the links of the track, the gripping pads are therefore stably constrained inside the relative seating; they cannot be removed sideways due to the lateral clamps, nor lengthways because their faces and the inclined surfaces of the xe2x80x9cdove-tailedxe2x80x9d seating are coupled together through interference.
The gripping pads are released from the relative links by compressing the elastic means of the lateral clamps which in this way are released from the sides of the pads, and thus allow them to be extracted.
The arrangement of the lateral clamps and the reduced space available in proximity thereof means that the release operation is carried out manually, for the most part, possibly with the aid of appropriate tools.
This is necessary also to mount and clamp new gripping pads, making it practically impossible to automate the operations to replace the pads which are therefore very long and laborious, and entail a prolonged interruption of the production cycle and an increase in the overall costs of drawing.
The present Applicant has devised and embodied this invention to overcome these shortcomings and to obtain further advantages.
The invention is set forth and characterized in the respective main claims, while the dependent claims describe other characteristics of the invention.
The purpose of the invention is to achieve a track for the drawing assembly in drawing machines including rapid attachment/detachment means suitable to allow the operations to replace the gripping pads to be carried out quickly and easily, at the same time ensuring that the pads are stably and safely clamped to the relative links.
Another purpose of the invention is to allow the operations to replace the gripping pads of the tracks to be automated, so as to reduce to a minimum both the time taken to carry out these operations and also the manpower required.
In the track according to the invention each link comprises rapid attachment/detachment means suitable to selectively clamp the relative gripping pad in correspondence with a specific housing seating.
According to the invention, the rapid attachment/detachment means comprise a clamping element, arranged substantially orthogonal to the plane on which the track and the relative pad lie, and an activation element, or thruster element, arranged substantially transverse to said clamping element, and therefore substantially parallel to the plane on which the track lies, and cooperating therewith in constraining the pad.
The clamping element is constrained to the relative link so as to be able to move only in an axial direction.
In one embodiment of the invention, the clamping element has at least a segment comprising a cam profile, cooperating with a mating cam profile made on at least a segment of the thruster element.
In a first embodiment, the cam profiles consist respectively of a spherical or semi-spherical element solid with the clamping element and by a mating curved or semi-spherical portion of the surface made on the thruster element. According to another embodiment, the cam profiles consist of mating inclined planes.
The thruster element is arranged in a lateral position on the relative link, accessible laterally with respect thereto and is also axially movable, transversely to the axis of the clamping element, at least from a first retracted position to a second advanced position.
The axial movement of the thruster element, in a direction substantially parallel to the plane on which the track and pad lie, causes its cam profile to slide on the corresponding cam profile of the clamping element, in such a manner as to define the clamped/unclamped conditions of the gripping pad to/from the relative track.
To be more exact, with the thruster element in a first position, the clamping element partially emerges from the relative link, and inserts itself into a mating positioning and constraining seating made on the gripping pad, and causes the latter to be clamped.
The movement of the thruster element into a second position, on the contrary, causes the clamping element to be axially displaced and therefore released from said positioning and constraining seating, and then to be retracted to a position of non-interference with the gripping pad; in this condition, the gripping pad is released and therefore can be removed from the relative track.
By the axial movement alone of the thruster element, the invention therefore allows to clamp/unclamp each gripping pad, allowing the operations to replace the pads to be carried out easily and rapidly.
The arrangement and lateral accessibility of the thruster element on the relative link also allows to install, in a position of non-interference with the drawing assembly and with the two relative tracks opposite each other, an automatic drive device for the thruster element, and possibly automatic pick-up and positioning means for the assembly/dis-assembly of the gripping pads onto/from the tracks of the drawing assembly. This allows to accelerate the operations to replace the gripping pads and therefore to reduce the time that the production cycle of the drawing machine is interrupted.